FI77867C - Process for preparation of antibacterial 5R, 6S, 8R-6- (1-hydroxyethyl) -2- (2-carbamoyloxyethylthio) penem-3-carboxylic acid and its pharmaceutically acceptable salt. - Google Patents

Abstract

There is disclosed the antibacterial 5R, 6S, 8R-6- (1-hydroxyethyl) -2- (2- carbamoyloxyethylthio) -penem-3- carboxylic acid, its pharmaceutically acceptable salts and metabolizable esters as well as compositions containing them and methods for their use, preferably the sodium salt for parenteral administration.

Description

1 77867

The method for preparing 5R, 6S, 8R-6- (1-hydroxyethyl) -2- (2-carbamoyloxyethylthio) penem-3-carboxylic acid and a pharmaceutically acceptable salt thereof is obtained from the antibacterial compound 5R, 6S, 8R- The present invention relates to a process for the preparation of 5R, 6S, 8R-6- (1-hydroxyethyl) -2- (1-hydroxyethyl) -2- (2-carbamoyloxyethylthio) penem-3-carboxylic acid and a pharmaceutical composition. (2-Carbamoyloxy-ethylthio) penem-3-carboxylic acid and a pharmaceutically acceptable salt thereof.

As used herein, "pharmaceutically acceptable salts" best mean alkali metal salts such as sodium and potassium salts; alkaline earth metal salts such as calcium, magnesium and aluminum salts; amine salts formed from a wide variety of suitable organic amines, i. aliphatic, cycloaliphatic, (cycloaliphatic) aliphatic or araliphatic primary, secondary or tertiary mono-, di- or polyamines or heterocyclic amines, for example salts derived from triethylamine (2-hydroxyethyl), 2-hydroxyethyl , tri- (O- (hydroxyethyl) -amine, 4-aminobenzoic acid 2-diethylaminoethyl ester, 1-ethylpiperidine, dicyclohexylamine, Ν, Ν-dibenzylethylenediamine, pyridine, collidine, 1-quinoline, quinoline, prochin, efenamine (β-methylamino-Λ-phenyl-benzeneethanol) and N-alkylpiperidine.

2 77867

Similar compounds are disclosed in Japanese Patent Application 56-142739. We have found that the compounds of the present invention surprisingly have better activity against gram-negative and gram-positive bacteria than the penem compounds disclosed so far. In addition, the compounds of this invention have low protein binding and their metabolites have only a slight or no unpleasant odor.

When tested in standardized microbiological assays, the compounds of this invention are active against gram-positive organisms such as Staphylococcus epidermis and Baccillus subtilis and gram-negative organisms such as E. coli and Salmonella at concentrations of 0.6 to 2.0 micrograms / ml. In addition, they are active against organisms that produce beta-lactamases, for example penicillinase and cephalosporinase, which is a sign of resistance to these enzymes. For example, the sodium salt is active against E. coli 74081501 (a beta-lactase-producing organism) at a test concentration of 0.1250 micrograms / ml.

As the antibacterial agent, the compounds of this invention are suitably formulated for oral, parenteral, topical and transdermal use, preferably for parenteral use. The scope of the present invention thus encompasses pharmaceutical compositions comprising the compounds of this invention in admixture with a pharmaceutically acceptable carrier or excipient.

; * In said compositions, the "compounds of this invention may be used as the sole active antibacterial agent or in combination with other antibacterial agents, enzyme inhibitors and / or absorption enhancers.

In a preferred composition for parenteral administration, the compound of the invention may be formulated into a solution or suspension. Typical topical formulations include solutions, creams, ointments, sprays, and mechanical delivery devices, for example, transdermal devices. For oral administration, the compounds of this invention are typically formulated as tablets, capsules, elixirs, or the like.

In addition to pharmaceutically acceptable carriers, other non-toxic compatible excipients, binders, disintegrants and lubricants commonly used in pharmaceutical formulations may be included. The compositions may also contain preservatives, thickeners, suspending agents, dispersing agents, emulsifying agents, wetting agents, stabilizing agents, and buffers.

The administration of a compound of this invention will be in accordance with the instructions of the attending physician and will depend on many factors, i. the age and weight of the subject to be treated, the route of administration, and the type and severity of the bacterial infection to be prevented or alleviated. The dosage per day is typically in the range of about 25 to 160 mg / kg, and preferably about 50 to 100 mg / kg in divided doses.

Dosage is typically in dosage units containing appropriate amounts, for example 0.250, 0.500, 1 or 2 g of active ingredient in association with a suitable physiologically acceptable carrier or diluent.

The process according to the invention for the preparation of the compounds of the formula I and their pharmaceutically acceptable salts and esters is characterized in that A) The compound of the general formula I 4 77867 OPg

1-r f SCH.CH OH

I 1 / j — N— \ 0 COOP r wherein Pg is a hydroxy protecting group and Pr is a carboxy protecting group, is reacted for 1 time with succinate in the presence of trifluoroacetic acid or trichloroacetic acid; B) Compound of general formula II OH 0 11

f- N * -X

O COOH

wherein R is an organic radical other than carbamoyloxyethyl and any groups are protected, if necessary or desired, by reacting a compound of general formula III

.:: O

II

HS-CH 2 CH 2 O-C-NH 2 111 or a reactive derivative thereof; C) A compound having the general formula 5 77867

OH 9K

I 1

s X \ T __ / S S

I '== - r I ^ ^ N \ # N \ ΛΛ

0 COOH 0 C00H

IVa TVb in which any functional groups are protected, if necessary or desired, is reacted with a compound of general formula V

O

Il V

L-CH CH 2 O-C-NH 2 - wherein L is a leaving group, D) A compound of general formula VI

O

OH | l

I S-CH CH O-C-NH

_

| 11 VI

S -

/ "SVS

0 = C-0H

wherein any functional groups, if necessary or desired, are reacted with a trivalent organophosphorus compound, followed, if necessary or desired, by methods A, B, C or D, one or more of the following: (i) deprotection of one or more protected groups; 6 77867

Method A

is generally carried out in an organic solvent, for example benzene or methylene chloride at a temperature of 0 to 35 ° C, preferably at about 25 ° C, for example at room temperature. The preferred solvent is methylene chloride. Preferred alkali metal cyanates are potassium and sodium cyanate. The recommended acid is trifluoroacetic acid.

Method B

involving the substitution of sulfoxides is usually carried out in an inert solvent, for example dichloromethane or tetrahydrofuran. The reaction is usually carried out under cooling, for example at -70 to + 10 ° C, preferably at 0 to + 5 ° C.

When the thiol compound itself is used, the reaction is generally carried out in the presence of a base, for example an organic base such as diisopropylethylamine or triethylamine, or an organic base such as potassium hydroxide or sodium hydroxide. Alternatively, a reactive derivative of a thiol, for example an alkali metal salt, preferably a sodium or potassium salt, may be used.

Method C

is generally carried out in a solvent, for example an organic solvent optionally containing water, for example acetonitrile and water, or in an anhydrous organic solvent such as tetrahydrofuran, ethyl ether or dioxane. The reaction is generally carried out in the presence of a base which may be an organic base, for example triethylamine, or more usually 7,77867 inorganic bases, such as sodium bicarbonate. Reaction temperatures are typically about -10 to + 45 ° C, for example 10 to 45 ° C, with room temperature (about 25 ° C) being preferred.

Preferred leaving groups L are halogen, for example iodine, trifluoroacetate and triphenylphosphonium oxy.

Method D, in which a compound of formula VI is cyclized, is usually carried out analogously to the method described in European Patent Application Publication No. 58317. It is thus usually carried out in an inert solvent, for example an aromatic hydrocarbon such as toluene, benzene, aliphatic ethers such as diethyl ether and dipropyl ether, cyclic ethers such as dioxane and tetrahydrofuran and halogenated hydrocarbons such as methylene chloride.

The cyclization reaction is generally carried out at temperatures between 20 and 80 ° C, usually between 40 and about 60 ° C for about 6 to 24 hours.

Suitable trivalent organophosphorus compounds include cyclic and / or acyclic trialkyl phosphites, triaryl phosphites and mixed arylalkyl phosphites or phosphoramides. Preferred trivalent organophosphorus compounds include trialkyl phosphites; triethyl phosphite is preferred.

In the process according to the invention, the carboxy group of the compounds (IVa, IVb), II and VI and the penem used as starting material in process A are generally protected in their respective processes. Thus, for example, the alkylation reaction of Method C yields a compound of the invention from a carboxy-protected derivative which must be subsequently deprotected. It may also be appropriate to protect the hydroxy group of hydroxyethyl attached to the 3-position of the azetidinone ring of these compounds.

Suitable hydroxy protecting groups Pg that can be used in the process of this invention include those conventionally used for this purpose in the context of β-lactams and which can be readily removed by methods using elemental zinc or by any other conventional method. Preferred hydroxy protecting groups include trichloroethyloxycarbonyl, dimethyltributylsilyl, trimethylsilyloxycarbonyl and trimethylsilyl; a particularly preferred protecting group is trimethylsilyl, which can be removed by treatment with a weak aqueous acid such as aqueous acetic acid.

Suitable carboxy protecting groups are those conventionally used in connection with penems and which can be removed under conventional conditions without reacting with other functional groups in the penem molecule, for example allyl, p-nitrobenzyl and trichloroethyl. The preferred carboxy protecting group is allyl.

The protecting group can be removed from the protected carboxyl group by a conventional method selected on the basis of the protecting group. To remove the preferred protecting group, allyl, this can generally be accomplished under catalytic conditions in the presence of a base, preferably by the methods described in our European Patent Application Publication No. 0013663. The allyl group is thus best removed using a suitable aprotic solvent such as tetrahydrofuran, diethyl ether or methylene chloride; sodium 2-ethylhexanoate (to give directly the alkali metal penem salt, preferably sodium 9,77867 or the potassium penem salt) or a carboxylic acid, preferably 2-ethylhexanoic acid (to give penem as the free acid) and using a mixture of a palladium compound and triphenylphosphine as a catalyst.

The above salts can be prepared by conventional methods to form salts of β-lactams such as penicillins / cephalosporins and penems.

The salts may be formed after deprotection of the allyl group as described above or, for example, by treatment of the free acid with metal compounds such as early metal salts of suitable carboxylic acids or ammonia or a suitable organic amine, with stoichiometric amounts or only a small excess being best used. Acid addition salts of a compound may be obtained in a conventional manner, for example by treating a compound of formula I with an acid or a suitable anion exchange reagent.

The salts can be converted in the usual manner to the free carboxy compounds, for example by treatment with tartaric acid / or other salts or pharmaceutically acceptable metabolizable esters.

The compounds of the invention may be prepared in optically active form using an optically active starting material in the reaction methods.

The compounds of the invention may also be prepared as mixtures of their stereoisomers, for example as racemic or diastereomeric mixtures. For example, the 5R, 6S, 8R isomer can be prepared in an amount equal to its enantiomer (mirror image), i. 5S, 6R, 8S when the starting compound is a racemic mixture. Stereoisomeric mixtures can be separated, if desired, by standard techniques. For example, the two enantiomers can be separated by fractional crystallization of optically active compounds, for example (-) - brucine or (+) - and (-) - ephedrine.

The compound I used in method A) can be easily prepared by the method described in European Patent Application, Publication No. 13662, i. by cyclizing the compound

X

and isopropanol

_, / 'S'-cxSv' R

3 H II

"X.

/ 1 Ίκν S

- N \ o x c- ¥ COOPr wherein R is optionally protected hydroxyethyl, Pr and Pg have the same meaning as above and Y is a conventional phosphono group in the Witting reaction, in particular a triaryl group, for example a triphenyl group. The reaction is generally carried out at a temperature between 30 and 60 ° C and preferably at reflux temperature in an organic solvent such as benzene, toluene or xylene under an inert atmosphere, for example under nitrogen or argon. The reaction time is, for example, 12 to 48 hours.

If R is protected hydroxyethyl, it is subsequently deprotected before being used in the process of the invention. By selecting the protecting group in a suitable manner, it can be selectively deprotected, leaving the Pg group in the position protecting the 5-hydroxy group.

The sulfinyl compound II used in the process Θ can be easily prepared by treating the compound of the general formula XI 77867

OH

^^ ΓΊ ^ ΪΓ s'R2 hi ». * _ *> / - N- \

O COOH

having an organic group other than carbamoyloxyethyl, with a mild oxidizing agent, for example m-chloroperoxybenzoic acid in an inert solvent, for example dichloromethane, between -30 ° C and 20 ° C, for example 0-5 ° C.

The 3-carboxy group and the 8-hydroxy group may, if desired, be in protected form. Such a compound of formula XI may be prepared by methods well known in the penem literature, for example by the method disclosed in European Patent Applications, publications 13662 and 58317.

The tautomeric compound of formula (IVa, IVb) can be prepared by the methods described in European Patent Application 83111615.7.

In the preferred form of this method: a) azetidinone of formula XX H «SR3 H /// Q m H-C7»

O XH

having a sulfur protecting group, for example triphenylmethyl, is reacted with an α-substituent of formula XXI. - 12 77867 with imported alkyl acetate

O

of

WCH2C-OCH2CH = CH2 XXI

wherein W is a leaving group, for example iodine or bromine, to form a compound of formula XXII SR ’Π ς /// 1 .. ^

XXII

This reaction can be carried out at 15 to 30 ° C in the presence of an acid acceptor. The reaction is best carried out in acetonitrile using cesium carbonate or tetraalkylammonium hydroxide as the acid acceptor.

b) The compound of formula XXII is treated with a stoichiometric excess of elemental zinc in hydrochloric acid in a suitable organic solvent such as tetrahydrofuran at 15-25 ° C to give the compound of formula XXIII

OH * K

\ r / 5n h „.L · -

u r / XXIII

H3C 2-4 * o-oo X "CH C-OCH2CH5CH2" 77867 c) The hydroxy group in the 5-position is protected with a trimethylsilyl group by reacting XXIII with bis-trimethylsilylacetamide; the reaction is conveniently carried out in a solvent such as dimethylformamide: d) The resulting protected compound is reacted with a thiocarbonyl compound of formula XXIV

S = C (¥) £ XXIV

wherein Y is a leaving group such as naphthyloxy or imidazolyl, generally using the same solvent as in the previous step, at a temperature between 10 and 45 ° C to form compound XXV

S

| H tl I * oFg H ^ s-c-y h c

/ XXV

H, C7 n

// N \ H

CH2C-OC-H2CH = CH2 where Pg is trimethylsilyl and Y is as defined above.

c) Compound XXV is treated with an equal molar amount of a strong base such as lithium diisopropylamide to give compound (IVa, IVb) · The reaction is generally carried out in an anhydrous inert organic solvent such as tetrahydrofuran by adding the base to a solution of compound XXV in a solvent; typical reaction temperatures are -50 to 100 ° C and the reaction is usually completed within 5 minutes to -24 hours.

In addition to allyl, other carboxy-protecting groups known in connection with penems, such as p-nitrobenzyl, can also be used as the carboxy group protecting group.

The starting compounds VI of process D) are best prepared by reacting a compound of formula XXV

is O

^ S \ cxS-ch2ch2o-c1-nh2 s sr

} NH

O

to react with a reactive derivative of an acid of formula XXVI, for example chloride

O

O i _

Pr-o-c / XOH BU- where Pr has the same meaning as above. This reaction is usually carried out under normal acylation conditions, i. in an inert solvent, for example methylene chloride, and in the presence of a base, for example an organic base such as a tertiary amine, for example diisopropylethylamine, optionally together with an inorganic base, for example calcium carbonate.

Such a method is described in more detail in European Patent Application, Publication No. 58317.

778 6 7

PREPARATION EXAMPLE A

Allyl (5R, 6S, 8R) -2- (ethanesulfinyl) -6- (hydroxyethyl) penem-3-carboxylate

A solution of allyl (5R, 6S, 8R) -2-ethylthio-6- (1-hydroxyethyl) penem-3-carboxylate (31.5 g) in ethyl acetate (200 ml) and dichloromethane (100 ml) is stirred at 0-5 ° A solution of m-chloroperoxybenzoic acid (80-85? 22 g) in ethyl acetate (120 ml) is added over 30 minutes. After 30 minutes, the solution is added to a stirred mixture of ethyl acetate (150 ml), water (125 ml) and sodium bicarbonate (15 g) and stirred rapidly for 15 minutes. The organic phase is dried over magnesium sulfate, evaporated and flash chromatographed on silica gel, eluting with 1: 1 hexane-ethyl acetate and then with pure ethyl acetate. The product fractions are evaporated and the residue is evaporated under high vacuum to give the title compound as a thick yellow oil.

NMR (CDCl 3): δ 1.2-1.6 (m, 6H), 3.0-3.35 (m, 2H), 3.38 (broad, 1H, b.p. D 2 O), 383 (m , 1H), 4.18 (m, 1H), 4.75 (broad d, J = 6.5Hz), 5.2-5.6 (m, 2H), 5.73 and 5.89 (both d Δ = 1.5 Hz, total 1H) and 5.8-6.2 (m, 1H).

PREPARATION EXAMPLE B

A) Potassium carbamoyloxyethyl trithiocarbonate

A solution of potassium hydroxide (0.132 g) in ethanol (5 ml) is added at 0-5 ° C with stirring and under nitrogen to a solution of mercaptoethanol carbamate (0.3 g) in ethanol and carbon disulphide (0.56 g). After stirring for 30 minutes, ether is added to the reaction solution, the title compound obtained is collected as a yellow powder and dried. Yield 0.52 g.

16 77867 B 3- (1- (2,2,2-Trichloroethoxycarbonyloxy) ethyl-4- (carbamoyloxyethylthiocarbonothioylthio) -azetidin-2-one 1 g of the potassium carbamoyloxyethyl trithiocarbonate obtained from step A) is dissolved in 20 ml of 90% ethanol, each contains 0.5 ml of carbon disulphide and 0.8 ml of triethylamine. The solution is cooled to 0-5 ° C and stirred under nitrogen. To the reaction mixture is added 1.2 g of 3- (1- (2,2,2-trichloroethoxycarbonyloxyethyl) -4-acetoxyazetidin-2-one in 12 ml of methylene chloride, the reaction mixture is stirred for 10 minutes and then diluted with ethyl acetate. aqueous citric acid followed by water and dried over magnesium sulphate The dried extract is evaporated and the crude product obtained is chromatographed on silica gel eluting with ethyl acetate: hexane (1: 1) to give 1.02 g of the title compound as a yellow oil.

C) 1- (2-Allyloxy-η 2 -dioxoethyl) -3- (1- (2,2,2-trichloroethoxycarbonyl) ethyl) -4-carbamoyloxyethylthiocarbonothioylthioazetidin-2-one

A solution of the title compound from Step B (0.45 g) in a mixture of methylene chloride (3 ml) and allyloxyacyl chloride (0.14 ml) containing calcium carbonate (0.4 g) is cooled to 0 ° C and stirred under nitrogen while adding dropwise di solution of -isopropylethylamine (0.19 ml) in methylene chloride (1 ml). After 10 minutes, 5 ml of ice water are added to the reaction solution with vigorous stirring and the mixture is filtered. The filtrate is separated, the organic layer is dried over magnesium sulfate and diluted with ethanol-free chloroform. The resulting solution of the title compound can then be used directly in the intramolecular cyclization of the title compound described below.

17 77867 EXAMPLE 1

SODIUM (5R, 65,8R) -2- (2-CARBAMQYloxyethylthiol) -6- (1-HYDROXYETHYL) -PENEME-3-CARBOXYLATE

A) Allyl (5R, 6S, 8R) -2- (2-carbamoyloxyethylthio) -6- (1- (trichloroethoxycarbonyloxy) ethyl penem-3-carboxylate.

A mixture of 0.80 g of powdered potassium cyanate and 1.1 g of allyl (5R, 6S, 8R) -6- (1- (trichloroethoxycarbonyloxy) ethyl) -2- (2-hydroxyethylthio) penem-3- carboxylate in 5 ml of methylene chloride, stirred at 0 -5 ° C and 1.1 g of trifluoroacetic acid are added dropwise. The mixture is stirred for 30 minutes at 0-5 ° C and then for 6 hours at 25 ° C. Aqueous CH 2 Cl 2 is treated with aqueous NaHCO 3, then dried, evaporated and the organic phase is chromatographed on silica gel in ether-CH 2 Cl 2 to give the title compound as a yellow oil.

IR spectrum (CH 2 Cl 2 solution) v max 3500, 1795, 1750 and 1700 cm -1. NMR (COCl 3: δ 1.53 (d, 3, J = 7), 3.22 (m, 2), 3.90 (dd, 1, J = 1.5 and 8.5), 4.32 ( d, 2, J = 7), 4.79 (s, 2), 4.5-5.0 (m, 4), 5.05-5.55 (m, 2), 5.66 (d, 1, J = 1.5) and 5.7-6.2 (m, 1).

B) Allyl (5R, 6S, 8R) -2- (2-carbamoyloxyethylthio) -6- (1-hydroxyethyl penem-3-carboxylate.

A mixture of 0.47 g of the product of step A, 0.45 g of zinc dust, 0.6 ml of acetic acid, 0.6 ml of water and 6 ml of tetrahydrofuran (THF) is stirred for 2 hours at 25 ° C. Work up in ethyl acetate-water, dry and evaporate the organic phase, then thin-layer chromatography using a mixture of 25% by volume of ether, ie 778 67 of ether and dichloromethane, to give the title compound as a pale yellow foam.

IR spectrum (CH 2 Cl 2 / J 6 max 3400, 1790, 1710 and 1690 cm -1; 1 H NMR (DMSO-d 6): δ 1.13 (d, 2, J = 7), 3.20 (m, 2 ), 3.85 (m, 2), 4.14 (t, 2, J = 7), 5.64 (m, 2), 5.1-5.5 (m, 2), 5.71 ( d, 1.3 = 1.5), 5.7-6.2 (m, 1) and 6.55 (broad s, 2, exchange D2O).

C) A mixture of 1.2 g of the compound prepared in step B, 0.55 g of sodium 2-ethylhexanoate, 0.12 g of triphenylphosphine and 40 ml of dry tetrahydrofuran is stirred under nitrogen at 25 ° C. 0.12 g of tetrakis (triphenylphosphine) palladium is added, then stirred for 2 hours and 100 ml of ether are added, centrifuged and washed with ethyl acetate. The resulting salt is dissolved in water and chromatographed on 10 g of reverse-phase C-18 silica eluting with water. The pure fractions are combined and lyophilized to give the title compound as a pale yellow powder.

IR (Nujoi Mull) v max 3500, 1775, 1700 and 1650-1600 cm -1.

EXAMPLE 2

SODIUM (5R, 65,8R) -2- (2-CARBAMOYloxyethyl TIP) -6- (1-HYDROXYETHYL) -PENEME-3-CARBOXYLATE

A) Allyl (5R, 6S, 8R) -2- (2-carbamoyloxyethylthio) -6- (1-hydroxyethyl) penem-3-carboxylate

A mixture of 1.8 g of 2- (carbasmoyloxy) ethanethiol, 4.4 g of the product of Preparation Example A and 80 ml of dichloromethane is stirred for 1 hour at 0-5 ° C while adding. . 1.6 ml of diisopropylethylamine. The mixture is chromatographed on silica gel, eluting with increasing concentration of acetone (5-15 [mu] l) in CH2Cl2. The pure fractions are evaporated to give the title compound as a pale yellow solid which is identical to the product obtained in Example 1, Step B.

B) The product of step A is then deprotected by the method of step C of Example 1 to give the title compound.

EXAMPLE 3

Sodium (5R165t8R) -6- (1-hydroxyethyl) -2- (carbamoyloxyethylthio) penem-3-carboxylate A) To the flask is added 0.5 g of an equilibrium mixture containing allyl (5R, 6S, 8R) -6- ( 1-hydroxyethyl) -2-thione penem-3-carboxylate and allyl (5R, 6S, 8R) -6- (1-hydroxyethyl) -2-thiolipenem-3-carboxylate, 0.45 g of 2-carbamoyloxyethyl iodide, 10 ml of acetonitrile, 5 ml of water and 0.2 g of sodium bicarbonate. The mixture is stirred for 2 hours at room temperature to give 0.55 g of allyl (5R, 6S, 8R) -3- (1-hydroxyethyl) -2- (2-carbamoyloxyethylthio) penem-3-carboxylate. Work up in ethyl acetate-water, dry, evaporate the organic phase and then chromatograph on thin-layer using a mixture of ether and dichloromethane containing 25% by volume of ether.

B) The product of step A) is deprotected as described in step C of Example 1 to give the title compound.

20 77867 EXAMPLE 4

Sodium (5Rt6St8R) -6- (1-hydroxyethyl) -2-carbamoyloxyethylthio) penem-3-carboxylate A) The solution obtained in Preparative Example B) is refluxed with stirring while triethyl phosphite (0.4 ml) is added over 2 hours. solution in chloroform (5 ml). Reflux is continued for a further 2 hours and then the solvent is evaporated off under reduced pressure. The residual oil is chromatographed on silica gel eluting with ethyl acetate-hexane (1: 4) to give 0.24 g of allyl- (5R, 6S, 8R) -3- (1- (1,1,1-trichloroethoxycarbonyloxy) ethyl) -2- (carbamoyloxyethyl thio) -penem-3-carboxylate.

IR: 5.62 μ NMR: (CDCl 3): 1.5 (d, J = 7cps) 3.10 (dt, J = J = 6.3cps) 3.90 (dd, JsJ = 7.5.1), 5cps) 4.25 (r, J = 6cps) 4.85 (s) 5.65 (d, J = 1.5cps) B) Cool to 0 ° C under nitrogen the penem product from step A) (0.45 g ) in tetrahydrofuran (5 ml) containing water (0.8 ml) and acetic acid (1 ml) and zinc dust (1 g) is added in small portions with stirring. After stirring for 1.5 hours, the solution is filtered, the filtrate is evaporated under reduced pressure and the residue is dissolved in ethyl acetate. The resulting solution is washed successively with water, aqueous sodium bicarbonate and brine, dried over magnesium sulfate and evaporated to dryness. The residue is crystallized from ethyl acetate: hexane to give 0.273 g of allyl (5R, 6S, 8R) -3- (1-hydroxyethyl) -2-carbamoyloxyethylthio) penem-3-carboxylate.

C) The penem product of step B) is treated by the method of step C of Example 1 to give the title compound.

Claims (3)

A process for the preparation of an antibacterial 5R, 6S, 8R-6- (1-hydroxyethyl) -2- (2-carbamoyloxyethylthio) penem-3-carboxylic acid and its pharmaceutically acceptable site, characterized in that A) a compound of the general formula I OPgg pSCH₂CH₂OH <O-N - (I) COOPr where Pg is a protecting group for the hydroxy group and Pr is a protecting group for the carboxy group is reacted with alkali metal cyanate in the presence of trifluoroacetic acid or trichloroacetic acid; B) a compound of general formula II OH f lps R (II) & N 2 C00H where R is any other organic radical than carbamoyloxyethyl and where any functional groups are protected, is reacted with a compound of general formula III if necessary 0 HS-CH 2 CH 2 O-ONH 2 (m) or with its reactive derivative; C) a compound of the general form OH OH "V'r" - "Vf'T · 0 ^" N "AoOH ^ ~ C00H IVa IVb where any functional groups are protected, when reacted, is reacted with a compound with the general form In V 0 H L-CH 2 CH 2 O-C-NH 2 (V) where L is a decisive group, D) a compound of the general formula VI OH 0 A-S-CH 2 CH 2 O-C-NH 2 I (VI) - v 0 = C-0H where any functional groups are protected, when required, are reacted with a three-valent organophosphorus compound, where necessary, following procedures A, B, C or D, one or more of the following measures: (i) the protection is removed from one or more protected groups;